1. Field of the Invention
The present invention relates to a marking device configured for irradiating a vertical or horizontal line laser to a surface of the subject to be irradiated by diffusing light flux only in a single direction from a light source such as semiconductor laser, particularly related to the impact absorption structure thereof.
2. Related Background of the Invention
In a construction site, used is an optical marking device irradiating a vertical line light or a horizontal line light which is a criterion of a vertical degree and a horizontal degree of pillars and walls. Most of the light sources of the optical marking device are semiconductor lasers and are generally referred to as a laser marking device. The laser marking device suspends a mechanism referred to as a gimbal mechanism or a gyro mechanism (hereinafter referred to as “gimbal mechanism”) in a perpendicular orientation so as to always maintain a vertical position and supports a light source unit including the semiconductor laser with the above mentioned light source unit holder. The light source unit includes a semiconductor laser as a light source, a collimating lens converting dispersing light radiated from the semiconductor laser into a parallel light flux, and a rod lens dispersing the parallel flux in a single direction. The parallel light flux enters into the rod lens from a direction perpendicular to a center axis thereof and is diffused in a fan shape only in a direction perpendicular to the above mentioned center axis by refraction by the rod lens. This diffusion light is irradiated to walls, ceilings, and floors of the building so as to draw straight lines by radiated light. Then a vertical line light can be irradiated by mounting the above mentioned light source unit on the above mentioned unit holder in such way that the center axis of the rod lens is horizontal. In addition a horizontal line light can be irradiated by mounting the above mentioned light source unit on the above mentioned unit holder in such way that the center axis of the rode lens is horizontal. Such is a fundamental principle of the laser marking device.
In the laser marking device, the light source unit holder supporting the light source unit is swingably supported by the gimbal mechanism. The laser marking device is required to accurately irradiate light of a vertical or horizontal direction line. For that reason, the gimbal mechanism desirably has a low friction resistance and the light source holder is desired to be maintained in a predetermined vertical direction position. Therefore, generally a bearing portion of the gimbal mechanism mainly comprises a ball bearing and an axis rotatably supported thereby. However, since potentially the lowest friction resistance is selected for the ball bearing employed in the gimbal mechanism of the laser marking device, a problem of impact resistance exists. Therefore, even in the case that the laser marking device is erroneously dropped down during use, the bearing portion is damaged adversely affected due to impact resistance to increase the friction resistance such that the light source unit holder cannot hold the predetermined position, which thus causes a problem of deteriorated accuracy of the irradiated line light.
In view of the foregoing, there has been proposed a laser marking device comprising a first support for swingably journaling a laser beam irradiating device with a first support shaft, a second support for swingably journaling the first support with a second support shaft perpendicular to the first support shaft, and a supporting member provided with a holding portion for holding the second support, wherein the second support is held on the above mentioned holding portion in such way that interference bodies are interposed respectively on both sides along longitudinal, lateral and vertical directions of the second support (ref. to, for example, Patent Reference 1, discussed below). The above mentioned “laser beam irradiation device” is the member corresponding to “light source unit holder” mentioned above. The first support shaft, the second support shaft and the second support comprise a gimbal mechanism. The above impact absorber reduces the impact otherwise applied to the above mentioned holding portion to transmit to the light source unit holder which is swingably journaled by the above mentioned gimbal mechanism, thereby reducing the damage to the gimbal mechanism.
The invention of the Patent Reference 1 is effective in protecting the gimbal mechanism when the laser marking device is dropped. However, the configuration of the above mentioned impact absorber of the Patent Reference 1 invention is required to entirely cover the exterior surface, top and bottom surfaces, and both side surfaces of the second support, which therefore increases the area and a volume of the impact absorber and thus increases the cost of the impact absorber. In addition, the volume of the laser marking device also increases due to the presence of the impact absorber. Moreover, there are many which are interfered with, such as the gimbal mechanism, the light source unit holder as well as the second support, for which impact absorbing effect should be improved. These factors also increase the volume of impact absorber.
Patent Reference 1 referred to above is Japanese Patent 2004-301756 A.
The present inventor proposes a marking device in which an impact absorber held by a support covers periphery of both ends of a shaft having a gimbal mechanism and above mentioned shaft is supported by the support through this impact absorber. That is an invention related to Japanese Patent Application 2005-64234.
According to the invention related to the above mentioned application, impact absorption effect is provided as expected. However, assuming that it is used under the severe conditions in dropping from a high location e.g. more than 1 m, it is found that even the invention related to the above mentioned application can not obtain a sufficient impact absorption effect.